• Smart Structures and Systems
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• 제19권5호
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• pp.499-512
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• 2017

Traditional structural dynamic analysis and Structural Health Monitoring (SHM) of large scale concrete civil structures rely on manufactured embedding transducers to obtain structural dynamic properties. However, the embedding of manufactured transducers is very expensive and low efficiency for signal acquisition. In dynamic structural analysis and SHM areas, piezoelectric transducers are more and more popular due to the advantages like quick response, low cost and adaptability to different sizes. In this paper, the applicable feasibility assessment of the designed "artificial" piezoelectric transducers called Concrete Piezoelectric Smart Module (CPSM) in dynamic structural analysis is performed via three major experiments. Experimental Modal Analysis (EMA) based on Ibrahim Time Domain (ITD) Method is applied to experimentally extract modal parameters. Numerical modal analysis by finite element method (FEM) modeling is also performed for comparison. First ten order modal parameters are identified by EMA using CPSMs, PCBs and FEM modeling. Comparisons are made between CPSMs and PCBs, between FEM and CPSMs extracted modal parameters. Results show that Power Spectral Density by CPSMs and PCBs are similar, CPSMs acquired signal amplitudes can be used to predict concrete compressive strength. Modal parameter (natural frequencies) identified from CPSMs acquired signal and PCBs acquired signal are different in a very small range (~3%), and extracted natural frequencies from CPSMs acquired signal and FEM results are in an allowable small range (~5%) as well. Therefore, CPSMs are applicable for signal acquisition of dynamic responses and can be used in dynamic modal analysis, structural health monitoring and related areas.

• Geomechanics and Engineering
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• 제19권3호
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• pp.283-293
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• 2019

Evaluating the stability of the excavation face of the cross-river shield tunnel with good accuracy is considered as a nonlinear and multivariable complex issue. Understanding the stability evaluation method of the shield tunnel excavation face is vital to operate and control the shield machine during shield tunneling. Considering the instability mechanism of the excavation face of the cross-river shield and the characteristics of this engineering, seven evaluation indexes of the stability of the excavation face were selected, i.e., the over-span ratio, buried depth of the tunnel, groundwater condition, soil permeability, internal friction angle, soil cohesion and advancing speed. The weight of each evaluation index was obtained by using the analytic hierarchy process and the entropy weight method. The evaluation model of the cross-river shield construction excavation face stability is established based on the idea point method. The feasibility of the evaluation model was verified by the engineering application in a cross-river shield tunnel project in China. Results obtained via the evaluation model are in good agreement with the actual construction situation. The proposed evaluation method is demonstrated as a promising and innovative method for the stability evaluation and safety construction of the cross-river shield tunnel engineerings.

• 한국전산구조공학회논문집
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• 제23권4호
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• pp.425-434
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• 2010

본 연구에서는 고층건물 구조시스템의 다양한 대안으로부터 이들의 성능을 합리적으로 평가하는 방안을 제안하였다. 대안평가는 업무절차에 따라 예비평가, 본평가, 실시평가로 나누어 수행된다. 대안평가를 위한 평가범주는 구조성능, 경제성, 공기의 세 가지로 구성되고, 각 평가범주는 이들을 평가하기 위한 세부 평가항목으로 구성된다. 예비평가에서는 경험지식에 의한 정성적인 평가를 수행하며, 본평가와 실시평가에서는 수치적인 결과를 바탕으로 주로 정량적인 평가를 수행한다. 평가결과의 종합화는 평가항목들간의 관계가 선형적이라는 가정하에 가중평균법을 적용하였다. 제안된 대안평가 방안은 실무예제에 대한 시뮬레이션을 통하여 그 적용성을 검토하였다.

• 한국전산구조공학회논문집
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• 제18권4호통권70호
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• pp.435-443
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• 2005

본 연구의 목적은 XML을 기반으로 하여 웹(web)을 통한 교환이 가능한 철관콘크리트 건물의 구조계산서를 전자화(digitalization)하는 방안을 제시하는 것이다. 이를 위해서 철근콘크리트 건물의 구조계산서를 XML로 표현하기 위한 자료 구조(data structure)를 정의하였다. 여기에는 수식과 그래픽 등 웹에서는 교환하기 어려운 형식의 자료들도 포함된다. 다음에는 이 자료구조에 따라 구조계산서를 XML문서로 작성하였다. 그리고 이 XML문서를 웹에서 효과적으로 출력(presentation)하는 방안을 도출하였다. 마지막에는 XML로 표현된 구조계산서를 웹에서 교환할 수 있는 웹 응용프로그램(web application)을 부분적으로 구현하였고, 이를 간단한 예제에 적용하여 본 연구결과의 타당성을 검토하였다.

• 한국전산구조공학회논문집
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• 제30권4호
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• pp.351-361
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• 2017

본 연구에서는 다양한 변수를 갖는 병렬 RC 구조벽체시스템에 대한 성능기반설계의 타당성과 이에 따른 모멘트 재분배 개념의 적용성을 분석하기 위해 횡력을 지지하는 병렬 RC 구조벽체시스템에 대한 비선형해석을 수행하였다. 설계변수(철근비, 콘크리트변형률, 벽체높이)가 병렬 RC 구조벽체시스템의 거동에 미치는 영향을 분석하였으며 이를 기반으로 병렬 RC 구조벽체시스템의 성능기반 설계를 위한 고려사항을 제안하였다. 비선형해석 결과, 병렬 RC 구조벽체시스템 성능기반 설계와 모멘트 재분배 개념의 적용을 위해서는 연결보의 항복여부에 대한 고려가 필요한 것으로 나타났다. 높은 벽체의 경우, 연결보가 항복하지 않고 탄성 상태로 거동할 수 있기 때문에 고층 병렬 RC 구조벽체시스템에 대해 성능기반 설계 및 모멘트 재분배 개념을 적용하기 위해서는 벽체에 높은 수준의 소성변형능력을 필요로 하며, 이를 위해 벽체 압축단부에 횡보강을 필수적으로 실시해야 한다.

• 국제초고층학회논문집
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• 제5권1호
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• pp.51-62
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• 2016

The concept of introducing viscous damping devices between outriggers and perimeter columns in tall buildings to provide supplementary damping and improve performance, reduce structural costs, and increase available usable area was developed and implemented by Smith and Willford (2007). It was recognized that the relative vertical movement that would occur between the ends of outriggers and columns, if they were not connected, could be used to generate damping. The movements, and correspondingly damping, can potentially be significantly increased by amplifying them using simple "mechanisms". The mechanisms also make it possible to increase the number of available dampers and thus further increase supplementary damping. The feasibility of mechanisms to amplify supplementary damping and enhance structural performance of tall, slender buildings is studied with particular focus on its efficacy in improving structural performance in wind loads.

• 비파괴검사학회지
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• 제32권6호
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• pp.678-685
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• 2012

The objective of this study is to monitor the health status of harbor caissons which have potential foundation damage. To obtain the objective, the following approaches are performed. Firstly, a structural damage monitoring(SDM) method is designed for interlocked multiple-caisson structures. The SDM method utilizes the change in modal strain energy to monitor the foundation damage in a target caisson unit. Secondly, a finite element model of a caisson system which consists of three caisson units is established to verify the feasibility of the proposed method. In the finite element simulation, the caisson units are constrained each other by shear-key connections. The health status of the caisson system against various levels of foundation damage is monitored by measuring relative modal displacements between the adjacent caissons.

• 항공우주시스템공학회지
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• 제6권1호
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• pp.13-18
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• 2012

This paper presents a structural health monitoring method of aircraft reciprocating engine using Principal Component Analysis (PCA) which analyzes vibration expressed by Averaged Normalized Power Spectral Density (ANPSD). Because ANPSD of the rotating shaft is sensitive to the rotating speed, this paper proposes to use a post-processing method of ANPSD is used to reduce the sensitivity. The PCA extracts compressed information from the post-processed ANPSDs and the information means the difference between current and normal cases of the engine. The experimental results demonstrate the feasibility and effectiveness of the proposed method to detect abnormal cases of the engine.

• 한국군사과학기술학회지
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• 제12권2호
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• pp.236-247
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• 2009

In Korea, the driving system restriction criteria is strictly applied(gross weight 400kN, axial load 100kN). Especially after the Seoungsu Bridge accident, safety factor has been strictly applied. The Safety factor is applied to the cumulative results for each steps like design, construction, maintenance of the Bridge. Because of it, the bridge is undervalued compared to its capacity. So, this generates loss for both private and military sector(eg. logistical delays, structural damage, etc.). But analyzing data from many existing researches we have confirmed that the military heavy vehicle may pass through the first class bridges. In consequence, this study have focused on determining whether HETS vehicles can pass over the first class bridge, without safety issues, using MIDAS structural analysis program. The results have confirmed that the military heavy vehicle may pass over the bridge.

• 한국공간구조학회논문집
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• 제16권4호
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• pp.53-58
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• 2016

SLIM AU(A plus U-shaped) composite beam was developed for reducing the story height in the residential buildings, and saving the cosrtuction cost of floor structures. Structural performance and economic feasibility of the composite beam have been sufficiently approved through the structural experiments and the analytical studies. However, the verification for fire safety is necessary for the practical application of the composite beam. The fire resistance tests with and without loading were performed for the fire safety verification, and the test results were summarized in this paper.